1. Field of the Invention
This invention relates to a security system for a compartment having a closure member. In particular, but not exclusively, the invention relates to a security system for the goods-carrying compartment of a commercial vehicle or truck provided with a closable access door, in order to permit monitoring of opening and closing of the access door.
In this specification, references to the sealing of a compartment are intended to mean that access to the compartment is restricted in a secure, verifiable and tamper-proof manner, rather than meaning the compartment is physically closed in such a way as to be airtight or watertight. In a case where the compartment has an access door, the sealing of that door may involve physically locking the door in a closed position, so long as when so closed, the maintenance of that state may be monitored by the security system.
2. Description of the Related Art
There are increasing concerns about ensuring the integrity of goods carried by commercial vehicles and trucks, in cargo containers as used on ships and on aircraft, and in other circumstances where the recipient of those goods wishes to be assured that they have not been tampered with, contaminated or otherwise spoiled following packing and dispatch from a warehouse, depot or manufacturing plant. Various systems have been developed in order to permit the sealing of a goods compartment whereby the integrity of that seal may be checked at the intended destination for the goods, to see whether access has been gained to the interior of the compartment.
In U.S. Pat. No. 4,766,419 (Hayward), there is disclosed a security device for use with the door of a cargo container or goods compartment. The device is activated by closing and sealing the door the container or compartment, and generates a random or pseudo-random number or code which is recorded both at the dispatch site and also on a sheet of paper which travels with the goods or otherwise is transferred to the destination. When the container arrives at the destination, the number displayed by the system may be compared that recorded at the dispatch site. Security may be enhanced by checking that number back to the dispatch site by a telecommunications link, and if the numbers all match, then the goods may be accepted. If the numbers do not match, then the compartment will have been opened on route between the dispatch site and the destination and the appropriate action taken, such as refusing delivery of the goods.
The above system suffers from the disadvantage of having to record the generated number or code, and then to ensure that the code is stored both at the dispatch site and is transferred to the destination. This leads to operator inconvenience, for all the personnel involved. An improvement of this security system is described in UK Patent Publication No. 2,368,174-A (Encrypta), but this is primarily concerned with effecting the seal, rather than determining the integrity of that seal whilst the compartment is in transit.
In UK Patent Publication No. 2,353,425-A (Maple et al), there is disclosed a security system for use with a GPS system, whereby the system allows opening of a goods compartment only when the GPS detects the compartment is located at a pre-programmed destination. If the compartment is opened elsewhere, the system records this and informs the recipient at the destination, who again may take the appropriate action. This system has the disadvantage that it requires programming with the co-ordinates of the or each destination at which goods are to be delivered, and also there may be a malfunction if such a destination has only a weak or no GPS signal.
Other security systems are to be found in U.S. Pat. No. 5,826,195 (Westerlage et al), which uses a cellular telephone network, and European Patent Publication No. 0,332,434-A (Security Services), which uses a wireless navigation system similar to GPS.